fix: add cast to exact type on field access (#729)

jadx-core/src/main/java/jadx/core/dex/instructions/IndexInsnNode.java

@@ -41,10 +41,15 @@ public class IndexInsnNode extends InsnNode {
 		switch (insnType) {
 			case CAST:
 			case CHECK_CAST:
-				return InsnUtils.formatOffset(offset) + ": "
-						+ InsnUtils.insnTypeToString(insnType)
-						+ getResult() + " = (" + InsnUtils.indexToString(index) + ") "
-						+ Utils.listToString(getArguments());
+				StringBuilder sb = new StringBuilder();
+				sb.append(InsnUtils.formatOffset(offset)).append(": ");
+				sb.append(insnType).append(' ');
+				if (getResult() != null) {
+					sb.append(getResult()).append(" = ");
+				}
+				sb.append('(').append(InsnUtils.indexToString(index)).append(") ");
+				sb.append(Utils.listToString(getArguments()));
+				return sb.toString();
 
 			default:
 				return super.toString() + ' ' + InsnUtils.indexToString(index);

jadx-core/src/main/java/jadx/core/dex/nodes/RootNode.java

@@ -30,6 +30,7 @@ import jadx.core.dex.nodes.utils.MethodUtils;
 import jadx.core.dex.nodes.utils.TypeUtils;
 import jadx.core.dex.visitors.DepthTraversal;
 import jadx.core.dex.visitors.IDexTreeVisitor;
+import jadx.core.dex.visitors.typeinference.TypeCompare;
 import jadx.core.dex.visitors.typeinference.TypeUpdate;
 import jadx.core.utils.CacheStorage;
 import jadx.core.utils.ErrorsCounter;
@@ -424,6 +425,10 @@ public class RootNode {
 		return typeUpdate;
 	}
 
+	public TypeCompare getTypeCompare() {
+		return typeUpdate.getTypeCompare();
+	}
+
 	public ICodeCache getCodeCache() {
 		return codeCache;
 	}

jadx-core/src/main/java/jadx/core/dex/visitors/ModVisitor.java

@@ -33,6 +33,7 @@ import jadx.core.dex.instructions.NewArrayNode;
 import jadx.core.dex.instructions.SwitchInsn;
 import jadx.core.dex.instructions.args.ArgType;
 import jadx.core.dex.instructions.args.InsnArg;
+import jadx.core.dex.instructions.args.InsnWrapArg;
 import jadx.core.dex.instructions.args.LiteralArg;
 import jadx.core.dex.instructions.args.NamedArg;
 import jadx.core.dex.instructions.args.RegisterArg;
@@ -49,6 +50,7 @@ import jadx.core.dex.trycatch.ExcHandlerAttr;
 import jadx.core.dex.trycatch.ExceptionHandler;
 import jadx.core.dex.visitors.regions.variables.ProcessVariables;
 import jadx.core.dex.visitors.shrink.CodeShrinkVisitor;
+import jadx.core.dex.visitors.typeinference.TypeCompareEnum;
 import jadx.core.utils.InsnRemover;
 import jadx.core.utils.InsnUtils;
 import jadx.core.utils.exceptions.JadxException;
@@ -144,6 +146,11 @@ public class ModVisitor extends AbstractVisitor {
 						fixPrimitiveCast(mth, block, i, insn);
 						break;
 
+					case IPUT:
+					case IGET:
+						fixTypeForFieldAccess(mth, (IndexInsnNode) insn);
+						break;
+
 					default:
 						break;
 				}
@@ -152,6 +159,31 @@ public class ModVisitor extends AbstractVisitor {
 		}
 	}
 
+	private static void fixTypeForFieldAccess(MethodNode mth, IndexInsnNode insn) {
+		InsnArg instanceArg = insn.getArg(insn.getType() == InsnType.IGET ? 0 : 1);
+		if (instanceArg.contains(AFlag.SUPER)) {
+			return;
+		}
+		if (instanceArg.isInsnWrap() && ((InsnWrapArg) instanceArg).getWrapInsn().getType() == InsnType.CAST) {
+			return;
+		}
+		FieldInfo fieldInfo = (FieldInfo) insn.getIndex();
+		ArgType clsType = fieldInfo.getDeclClass().getType();
+		ArgType instanceType = instanceArg.getType();
+		TypeCompareEnum result = mth.root().getTypeCompare().compareTypes(instanceType, clsType);
+		if (result.isEqual() || (result == TypeCompareEnum.NARROW_BY_GENERIC && !instanceType.isGenericType())) {
+			return;
+		}
+		IndexInsnNode castInsn = new IndexInsnNode(InsnType.CAST, clsType, 1);
+		castInsn.addArg(instanceArg.duplicate());
+		castInsn.add(AFlag.EXPLICIT_CAST);
+
+		InsnArg castArg = InsnArg.wrapInsnIntoArg(castInsn);
+		castArg.setType(clsType);
+		insn.replaceArg(instanceArg, castArg);
+		InsnRemover.unbindArgUsage(mth, instanceArg);
+	}
+
 	private static void replaceConstKeys(ClassNode parentClass, SwitchInsn insn) {
 		int[] keys = insn.getKeys();
 		int len = keys.length;

jadx-core/src/test/java/jadx/tests/integration/types/TestFieldAccess.java

+package jadx.tests.integration.types;
+
+import org.junit.jupiter.api.Test;
+
+import jadx.tests.api.IntegrationTest;
+
+import static jadx.tests.api.utils.assertj.JadxAssertions.assertThat;
+
+public class TestFieldAccess extends IntegrationTest {
+
+	public static class TestCls {
+		private String field;
+
+		static <T extends TestCls> T testPut(T t) {
+			((TestCls) t).field = "";
+			return t;
+		}
+
+		static <T extends TestCls> T testGet(T t) {
+			System.out.println(((TestCls) t).field);
+			return t;
+		}
+	}
+
+	@Test
+	public void test() {
+		assertThat(getClassNode(TestCls.class))
+				.code()
+				.doesNotContain("t.field");
+	}
+}